Method for making a bolometer



United States Pater 2,836,800 METHOD non MAKING A BOLOMETER John H. Rnhrhangh, Kew Gardens, N. Y., and Charles liiine, Kearny, and William G. Zoellner, East Orange, 1 .3.

Application December 19, 1955, Serial No. 554,057 2 Claims. (Cl. 333-22) This invention relates to a method for making a bolometer.

An object of the present invention is to provide a methed for making a bolometer which will detect radiation that is transmitted in one or more modes of oscillation.

Another object of the present invention is to provide a method for making a bolometer which enables the location of the Wollaston wire within the wave guide at a point most favorable to the frequency to be used.

A further object of the present invention is to provide a method for making a bolometer which is highly efiicient, and commercially practical.

A still further object of the present invention is to provide a method for making bolometer which has a higher degree of efliciency and a longer life of use than prior bolometers.

Other objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

Figures 1 to 6 illustrate graphically the steps of the method according to the present invention.

Figure 7 is a view in cross section of the bolometer of the present invention.

In carrying out the method of the present invention a wave guide section or a rectangular shaped pipe 10 is provided as illustrated in Figure l, the section having opposed walls 11 and 12 in each of which is a 'hole 13. The holes 13 are in registry with each other and are adjacent to one end 14 of the section 16. A piece of Wollaston Wire 15 consisting of a platinum core encased in a silver sleeve is threaded through the registering holes 13 with one end portion 16 exteriorly of one of the opposed walls or Wall 12 and with the other end portion 17 exteriorly of the other of the opposed walls or wall 11, as shown in Figure 2. The wire 15 is insulatingly anchored to the respective holes 13 so that the wire is held in strain free condition, as by causing a small amount of melted insulating wax, such as dental wax, to flow about the holes, the

wax in and about the holes and the adjacent portions of v the wire serving to anchor the wire in a strain free condition, as also shown in Figure 2.

The end portion 16 of the wire 15 has its end thereof electrically connected to the exterior face of the wall 12 as by means of a small amount of dental amalgam, while the end portion 17 of the wire 15 has its end thereof electrically connected as by means of dental amalgam to an anchor or metal block 18 insulatingly attached as by means of insulating wax to the exterior face of the wall 11 adjacent the hole 13, as illustrated in Figure 3. Thus, the Wave guide section becomes one electrical pole. Of course, when in use, the two terminals constituted by the electrically connected end portions 16 and 17 are connected to amplifying circuits of conventional design.

The part of the wire 15 held in strain free condition between the holes 13 in the section 10 is then treated so as to remove the silver sleeve and expose the platinum core. One way of eifeeting this treatment is electrolytically, employing an electrolyte of dilute nitric acid and containing a wetting agent to reduce surface tension, as for example, Aerosol. The progress of the treatment is observed continuously with the aid of an ohmmeter which is connected to the wire. After deplating or removal of the silver sleeve, the wave section is thoroughly washed to remove all acid. The washing may be done by either ethyl alcohol of strength or with water containing a wetting agent. A wetting agent is necessary for washing with water so as to maintain the platinum core without breaking. If no wetting agent is used, washing with water will cause the surface tension to break the platinum core. After deplating and washing the part ofthe wire 15 between the holes 13 has the platinum core 19 exposed, as shown in Figure 4.

Next, another wave guide section or rectangular shaped pipe 2% is arranged so that one end 21 is in longitudinal alignment with and adjacent to the one end 14 of the section 16', Figure 5, and the ends 21 and 14 of the sections 26 and 1d are joined together, preferably integrally, as by electroplating, soldering, or by efifecting the joindure by means of silver amalgam. This results in the assembly illustrated in Figure 6.

The other end 25 of the section 10 Figure 6 is closed by a plunger 26 which is electrically connected to the section 14), the plunger 26 being slidably movable back and forth in the section 10 by means of the screw 27, as illustrated in Figure 7. It is to be noted that the location of the wire 15 must be such that it is at an antinode with respect to the end 22 of the section 20 for standing waves in the Wave guide of the frequency to be detected or at an antinode with respect to the entire system employed, and that the other end 25 of the section 10 be electrically closed by the plunger 26. Adjustment of the plunger aids in producing a large voltage standing wave ratio with an antinode at the wire.

While it is preferred to operate the bolometer with the plunger closing the end opposite to that end having the wire adjacent thereto, it is to be understood that it can be operated with the plunger removed. In this case the standing wave pattern depends on reflection from external apparatus being used and an antinode at the Wollaston wire is produced by suitable longitudinal adjustments of the external apparatus.

Having thus described the invention what is new and desired to be secured by Letters Patent is:

1. A method for making a bolometer which comprises providing a wave guide section having opposed walls each provided with a hole, the holes being in registry with each other and adjacent to one end of said section, threading a piece of Wollaston wire consisting of a platinum core encased in a silver sleeve through said registering holes with one end portion exteriorly of one of said opposed walls and with the other end portion exteriorly of the other of said opposed walls, insulatingly anchoring said wire to the respective holes so that the wire is held in strain free condition, electrically connecting the end of said one Wire portion to the exterior face of said one opposed wall of said section, electrically connecting the end of said other wire portion to an anchor insulatingly attached to the exterior face of said other opposed wall of said section, treating the part of said wire held in strain free condition between said holes so as to remove the silver sleeve and expose the platinum core, arranging another wave guide section so that one end is in longitudinal alignment with and adjacent to said one end of said first named section, and joining together said one ends of said first named and said another wave sections, the location of said wire in said first named section being such that it is at an antiof the assembly of providing a wave guide'section having opposed walls each providedwith a hole, the holes being in registry with eachother and adjacent to one end of said section, threading a piece ofWollaston wire consisting of a platinum core encased in a silversleeve through said registeringholes with-one end portionexteriorly of one of said opposed walls and-with the-other end portion exteriorly of the other of said opposed Walls, insulatingly anchoring said wire to the respective holes so that the Wire is held in strain f ree condition, electrically connecting the end of said one wire portion to the exterior face of said one 0pposed wall of said section, electrically connecting the end of said other Wire portion to a metal block insulatingly attached to the' exterior face of said other opposed wall of said section, treating the part of said wire held instrain free condition between said holes 'so as. to removethe silver sleeve and expose the platinum core, arranging another wave guide section so that one end is in longitudi-r nal alignment with and adjacent to said one end of said first named section, and joining together said one ends of said first named and said another wave sections, the location of said Wire, in said first named section being such that it is at an antinode with respect to the other end of said another wave section. t

References Cited in the file of this patent" UNITED STATES PATENTS 

